This invention relates to a sheet distributor that receives sheets of a photographic material and the like as they are being transported after they were cut to a specified length and which then distributes those sheets so as to transport them in a plurality of lines. The invention also relates to an image recorder using such sheet distributor, as well as a sheet distributing method.
Printers operating on digital exposure have been put on the market in recent years. They are commonly called digital photoprinters and perform the following operations: the image recorded on a film is read photoelectrically and the image thus read is converted to digital signals which are subjected to various image processing steps to produce recording image data; the light-sensitive material is exposed by scanning with optical beams modulated in accordance with the image data so as to record an image (latent image), which is subjected to development and other necessary treatments to make a print (photograph) which is then output.
The digital photoprinter is basically composed of two parts, an input device having a scanner (image reader) and an image processing unit, and an output device having a printing unit (image recorder) and a processor (developing machine).
In the scanner, the projected light from the image recorded on a film is read photoelectrically with an image sensor such as a CCD sensor and sent as the image data for the film (image data signals) to the image processing unit. In the image processing unit, the image data is subjected to specified image processing steps and sent to the printing unit as image data (exposure conditions) for image recording.
In the printing unit, if it is of a type that operates on exposure by scanning with optical beams, a web of light-sensitive material in roll form is drawn by a specified length, cut to a sheet and transported to the exposing position. The optical beams modulated in accordance with the supplied image data are deflected in the main scanning direction while the cut sheet of light-sensitive material is transported in the auxiliary scanning direction which is perpendicular to the main scanning direction. In the processor, the exposed light-sensitive material is subjected to specified development and other necessary treatments to make a print that reproduces the image recorded on the film.
The digital photoprinter requires that a large volume of prints be output in high efficiency and to this end the light-sensitive material has to be exposed by scanning and developed within a short period of time. This raises the need to improve the efficiency of development and subsequent treatments and in order to perform those treatments on the light-sensitive material as it is being transported in a plurality of lines, various types of distributor have been proposed that can distribute sheets of the light-sensitive material into a plurality of lines for subsequent transport.
In the digital photoprinter, optical beams are scanned through a preset range of area in order to expose the light-sensitive material being transported and it is particularly desired that no image be recorded askew or off center (offset) on the light-sensitive material. From this viewpoint, post-exposure distributing is desired that distributes sheets of the as-exposed light-sensitive transport.
JP 9-329885 A discloses in paragraphs 0120–0129 and 0161–0165 a photographic printing and developing apparatus having a distributor by means of which sheets of photographic paper that have been preliminarily cut to a desired size and then exposed for printing are distributed for transport in two lines, right and left, downstream the transport path and which has a first roller pair and a second roller pair, each consisting of a driving roller and a driven roller, that are provided along the transport path, and a carriage for causing the first and second roller pairs to reciprocate to the right and left of the transport path.
Japanese Patent 3086985 discloses in paragraphs 0014–0017 a photographic distributor which receives exposed cut sheets of photographic paper and distribute them into a plurality of lines relative to the direction in which the photographic paper advances (the direction of its transport), with the distributed sheets of photographic paper being then fed, either simultaneously or consecutively, into an automatic developing machine connected or positioned downstream.
The distributors disclosed in those references are each intended for application to an analog photographic printing unit which performs exposure of the image on a film by directly printing it on photographic paper as the light-sensitive material using the projected light that has passed through the image. If such distributors are applied to the digital photoprinter under consideration, the following disadvantages will occur.
Those distributors each adopt a control sequence by which sheets of the exposed light-sensitive material in transport are brought to a temporary stop in the distributor, distributed right and left, and start to be transported again. This process consisting of transporting sheets of the light-sensitive material, bringing them to a stop, distributing them and transporting them again can be easily realized in the above-described analog photographic printing unit. To be more specific, the printing units disclosed in JP 9-329885 A and Japanese Patent 3086985 are analog photographic printing units that allow the image on a film to be directly printed on the light-sensitive material (photographic paper) by focusing projected light, so they have a control sequence that transports the light-sensitive material to the print position and brings it to a temporary stop for a sufficient period of time to perform printing. Hence, the analog photographic printing units have the advantage that a control sequence comprising the steps of transporting the light-sensitive material, bringing it to a stop and transporting it again can be easily incorporated into the distributor.
However, in the digital photoprinter, an image is recorded on the light-sensitive material in transport by scanning optical beams over it in a direction perpendicular to the direction in which it is being transported, so the control sequence involving the step of bringing the light-sensitive material to a temporary stop is absent. Alternatively, exposure is performed by a control sequence that controls the gap (distance) between successively transported sheets of light-sensitive material and development that follows exposure is also performed by a control sequence that controls the gap between successively transported sheets of light-sensitive material. Therefore, incorporating in the distributor an additional time-based control sequence that includes the step of bringing the light-sensitive material to a stop is extremely difficult in the technical development of practically feasible and cost-effective digital photoprinters.
Consider, for example, the step of unrolling a specified length of light-sensitive material and cutting it into sheets. This cutting step is performed at specified time intervals on the basis of the gap between sheets of light-sensitive material that was preliminarily set in accordance with the throughput of the exposing and developing processes. So if a transport stop time is provided for the distributor in the transport path of the light-sensitive material in the case of realizing the process in which sheets of the light-sensitive material are developed and otherwise treated as they are sequentially spaced apart in the direction of transport, the time interval of cutting the light-sensitive material must be controlled in consideration of the stop time and the control sequence becomes complicated.
In order to increase the throughput of print processing, the transport speed of the light-sensitive material may be increased. If, in this case, sheets of light-sensitive material are brought to a stop and distributed into a plurality of lines, they will be approached by ensuing sheets of light-sensitive material and this makes it necessary to increase the speed of distribution with the increasing speed of transport. In fact, however, the speed of distribution cannot be increased beyond a certain limit and the transport capacity is also limited.
In the distributor disclosed in JP 329885 A, the first roller pair and the second roller pair are designed to make sliding contact with the thrust bush in the carriage (see paragraph 0129 and FIG. 25), so the thrust bush and the rollers will wear away as the use of the distributor is prolonged. In consequence, as the transport speed increases, extra resistance may occur or the direction of transport may become significantly askew, leading to impaired durability. Thus, the distributors disclosed in JP 329885 A and Japanese Patent 3086985 are limited in the capacity of transporting the recording material and the durability of the former is low on account of the device configuration.